Notes: Agastache foeniculum (Anise Hyssop) is native prairie plant that is also found in Ontario. Agastache nepetoides (Yellow Giant Hyssop) and scrophulariifolia (Purple Giant Hyssop) are native across the Eastern states and provinces although they can be locally quite rare.

Agastache 'Blue Fortune'

Agastache foeniculum and Agastache scrophulariifolia are similar in appearance. However, Anise Hyssop only grows to about five feet tall while the other two native species grow up to 8 feet. Anise Hyssop has leaves that are strongly scented with Anise and each flower has a calyx that is the same colour as the flower itself. Agastache scrophularia has leaves with some Anise scent, but, each flower has a green calyx. The flowerheads are the most reliable way to identify the two species.

In natural settings, Agastache foeniculum grows in open spaces and requires the most light. Agastache nepetoides is the most shade tolerant, flowering with less than two hours of sunshine each day. All three species are somewhat drought tolerant, but may show signs of heat stress when subjected to direct sun during the middle of the day. The tips of each shoot droop, but can recover nicely.

Anise Hyssop is by far the most widely available species in garden centres. If you buy the native plant (usually in the herb section), it reseeds itself vigorously. However, if you buy a sterile cultivar like Blue Fortune (Usually in the perennial section), it will behave itself and still attract loads of insects. Blue Fortune has a tendency to flop over after heavy rain. Support it with surrounding plants or be prepared to prop it up.

Anise hyssop is the most attractive of the three native species as a garden plant because the blue calyxes makes the flowerheads colourful even when there are few flowers present. If you have shade, Yellow and Purple Giant Hyssops are still one of the best choices to attract insects in mid-summer and due to their size should be planted at the back of the border. Purple Giant Hyssop has a long flowering season and is also popular with hummingbirds. Yellow Giant Hyssop tends not to branch too much so it is necessary to plant several specimens 18 inches apart. Purple Giant Hyssop is large enough to be planted as a single specimen and works well as a companion to Cup Plant. I recommend Purple Giant Hyssop as a native alternative to Buddleia.

All other Agastache have trouble surviving winters in Ontario and should be treated as annuals. They are typically in the red to purple range and can be used to attract hummingbirds. The corollae in the three native species are short and the nectar is available to a wide range of pollinators including hummingbirds.

Agastache 'Apricot Sunrise' is a hybrid cultivar that hummingbirds stop to drink at. While the nectaries are out of reach to most insects, a small number will still take pollen from the anthers that extend out of the flower. This cultivar is smaller than Agastache foeniculum growing to around 30-36 inches.